Block-grinding apparatus

ABSTRACT

A grinding apparatus wherein a block to be abraded is transferred to and held on a constant load bed which, through pivotable connections and constant force fluid cylinders, maintain said block in engagement with an abrasive material and pivotably accommodates varying geometric shapes of blocks in order to control the grinding depth over the facial surface and thus minimize the removal of material required to permit all portions of a facial surface, although possibly irregular, to be abraded to at least a predetermined grinding depth.

United States Patent Inventor William J. MclDonald Stillwater Township, Washington County, Minn.

Appl. No. 818,657

Filed Apr. 23, 1969 Patented Sept. 7, 1971 Assign Minnesota Mining and Mnnulncturlng Company Saint Paul, Minn.

BLOCK-GRINDING APPARATUS 7 Claims, 8 Drawing Figs. I

US. Cl 51/138 Int. Cl B241) 21/12 Field of Search 51/76, 112,

[56] References Cited UNITED STATES PATENTS 3,271,909 9/1966 Rutt et a1. 51/138X 3,325,947 6/1967 Burt 51/138 3,394,501 7/1968 Carlson et al.... 51/138 3,415,017 12/1968 Murray 51/135 Primary Examiner-Theron E. Condon Assistant Examiner-Neil Abrams Att0rneyKinney, Alexander, Sell, Steldt & Delahunt ABSTRACT: A grinding apparatus wherein a block to be abraded is transferred to and held on a constant load bed which, through pivotable connections and constant force fluid cylinders, maintain said block in engagement with an abrasive material and pivotably accommodates varying geometric shapes of blocks in order to control the grinding depth over the facial surface and thus minimize the removal of material required to permit all portions of a facial surface, although possibly irregular, to be abraded to at least apredetermined grinding depth.

AT TOl-PNE vs FIG. 3

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INVENTOR. 6 MAM/m1 fiffia/vflm BY I W ATTORNEYS BLOCK-GRINDING APPARATUS BACKGROUND OF THE INVENTION Concrete building blocks, as they are commonly known in the building trade, are produced in a variety of physical sizes, shapes and compositions. The heavyweight block, used for constructing a load-bearing wall, is a dense, relatively nonporous composition whereas the lightweight block is of a relatively porous composition. Both types of block essentially contain a binder material mixed with an aggregate. The aggregate used with a heavyweight block will commonly have a high structural strength and, generally, extreme hardness.

The lack of physical uniformity in concrete building blocks has not caused problems in their use, except in extreme cases, because the mortar used in the normal method of construction allows compensation for such loose tolerances. Where it is necessary to produce a more accurately dimensioned concrete block, it is known to use a concrete block shaping and grinding apparatus. Such a grinding apparatus will grind the block to produce parallel facial surfaces, spaced a predetermined dimension apart, by passing the block through a relatively fixed grinding aperture. The abrasive material, whether it is an abrasive belt or wheel, is commonly constructed and used to grind at least one of the facial surfaces to a plane. Thus, a first facial surface of the block is forced against a planar support and the planar abrasive surface engages and grinds the opposing facial surface of the block, producing a precisely shaped concrete building block. The cost involved in so grinding a heavyweight concrete block, because of the difficulty and excessive time required to precisely shape such a composition,

normally prohibits any grinding of such blocks.

When a concrete building block is to be ground for aesthetic reasons, a facial surface is ground to a sufficient depth to reveal the colorful aggregate. The required depth is proportional to the size of the aggregate. The required depth is proportional to the size of the aggregate, i.e., a larger aggregate requires a deeper grind to sufficiently reveal the aggregate. The cost of producing coplanar facial surfaces, on any block ground for aesthetic reasons, becomes wastefully unreasonable for economic reasons. A more economic approach would be to remove a specified substantially uniform amount from an entire facial surface without necessarily producing a planar surface or coplanar surfaces.

When a facial surface of a relatively long sheet of material is to be ground, such as rolled steel stock, it is commonly known to use a floating support roll for causing a specified uniform amount to be ground from a facial surface without producing a ground planar surface. To use such an apparatus for grinding relatively short blocks, such as concrete building blocks, would cause unacceptable impact shattering of the blocks primarily because the block cannot be adequately supported during the grinding thereof.

SUMMARY OF THE INVENTION The present invention relates to a grinding apparatus and more particularly to a grinding apparatus for abrading a facial surface of a block and affords control of the grinding depth and accommodation to varying geometric shapes of said block in order to control the required grinding depth over said facial surface to permit all portions of said facial surface to be abraded to at least a predetermined grinding depth. Thus, the facial surface is ground to a sufficient depth to reveal the more colorful composition of the block and the ground depth longitudinally along said facial surface is controlled to minimize the removal of material from the entire facial surface of said block.

Thus, where the block is composed of a concrete-aggregate mixture, the minimization of facial surface removal results in displaying the colorful aggregate for satisfying decorative effects at an economically feasible cost. Likewise, with this apparatus, blocks of other compositions may be similarly finished.

Other uses and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing in which like numerals designate like parts throughout the figures and wherein:

FIG. 1 is a side elevational view, partly cut away, of the block-grinding apparatus;

FIG. 2 is a front view of the apparatus of FIG. I with parts cut away;

FIG. 3 is an enlarged fragmentary vertical sectional view taken along line 3-3 of FIG. 2 showing a concrete block partially abraded;

FIG. 4 is a top sectional view taken along line 4-4 of FIG.

FIG. 5 is a transverse sectional view taken along line 55 of FIG. 1;

FIG. 6 is a diagrammatic side elevational view of the apparatus of FIG. 1;

FIG. 7 illustrates a convex facial surface of a concrete block; and

FIG. 8 illustrates a concave facial surface of a concrete block.

Referring now to the preferred embodiment of FIG. 1, the portion of the apparatus to the right-hand side of F IG. 1 is the front portion of the apparatus whereas the opposite portion therefrom is the back or rear portion of the'apparatus. The side of the apparatus, in FIG. 1, nearest the viewer is the first side whereas the opposite side therefrom is the second side of the apparatus. As will become readily apparent, concrete blocks normally enter at the back portion of the apparatus, are advanced through the abrading assembly, and are ejected at the front portion of the apparatus.

The block-grinding apparatus 10 of FIG. 1 comprises a frame 12, conveyor means 20 to move the block 11 to be abraded along a predetermined longitudinal path from the back portion of the apparatus to the front portion, an abrading assembly 35 supported by said frame 12 and located adjacent to said conveyor means 20 along said predetermined path, a constant load means 50 pivotably supported by said frame 12 and located along said predetermined path opposite said abrading assembly 35 for affording a predetermined loading force 72 on said block 11 in transverse line contact against said abrading assembly 35 to control the grinding depth and for affording accommodation to varying geometric shapes of said block 11 in order to control the grinding depth over the facial surface 19 and thus minimize the removal of material required to permit all portions of said facial surface 19 to be abraded to at least a predetermined grinding depth, and holding means 60 secured to said constant load means 50 and spaced from said abrading assembly 35 to restrain tipping movement of said block 11 about itself caused by engagement with said abrading assembly 35.

The frame 12, as most clearly shown in FIGS. 1, 2 and 4, includes a first side frame 13, a second side frame 14, an end brace 15, a top brace 16, block supports 17 and a block chute 18.

The conveyor means 20, as most clearly shown in FIGS. 1 and 4, may comprise any apparatus which will move a block 11 alongv a predetermined longitudinal path past said abrading assembly 35 and is illustrated in the preferred embodiment as including a drive roll assembly 21, a driven roll assembly 26 and a conveyor belt 34. The drive roll assembly, as more clearly shown in FIGS. 2 and 4, includes a drive shaft 22 rotatably mounted on bearings (not shown) in each side frame l3, 14, a drive roll 23 rigidly secured to the drive shaft 22 and motor means, e.g. a motor 24, secured to the first side frame 13 and the drive shaft 22 for rotating the drive roll 23 at about 15 surface feet per minute. The driven roll assembly 26, as shown in FIGS. 1 and 4, includes a support shaft 27 slidably secured in the slide guides of each side frame 13, 14, by the slack and guide adjusters 28, see FIG. 4, and a driven roll 29 rotatably supported via bearings (not shown) on the support shaft 27. Each slack and guide adjuster 28 includes a spring 32, a threaded shaft 30, and a self-locking nut 31 for increasing or decreasing the spring force between the end brace and the nut 31. Thus, as the nut 31 adjacent the first side is threaded toward the end brace 15 the spring 32 is compressed and a larger force is exerted on the first side of the support shaft 27 to move the first side of the support shaft 27 toward the end of the apparatus 10. Likewise, the adjuster 28 adjacent the second side may be adjusted to remove any slack in the conveyor belt 34 and to guide or track the conveyor belt 34. The rubberlike conveyor belt 34, which extends about the drive and the driven roll assemblies 21, 26, includes cleats 33 extending across the lateral direction of the conveyor belt 34 to provide positive engagement between the belt and the concrete block 11 to be abraded. The motion of the concrete block 1 1, relative to the abrading assembly 35 should be maintained at a set speed, e.g., 15 feet per minute. A nonuniform speed of the block 11 past the abrading assembly 35 would cause uneven abrading of the facial surface 19.

The abrading assembly 35 includes a contact drum assembly 37 having a fixed axis of rotation extending transverse to said predetermined longitudinal path, an idler drum assembly 42, and abrasive material, e.g. an abrasive belt 45, supported by the contact drum 39 for abrading the facial surface 19 of a concrete block 11. The contact drum assembly 37 includes a supporting shaft 38 rotatably mounted on bearings (not shown) in each side frame 13, 14, a contact drum 39 having a substantially rigid cylindrical surface, e.g. steel, and rigidly secured to the shaft 38, and drive means, eg a drive motor 40, most clearly shown in FIG. 2, secured to the first side frame 13 and the supporting shaft 38 for rotating the contact drum 39 at about 9,000 surface feet per minute in a direction as indicated by arrow 68 which opposes the normal direction of the block 1 l. The idler drum assembly 42 includes a support shaft 43 slidably secured to the slide guides by the slack and guide adjusters 44, see FIGS. 1 and 2, and bearings (not shown) within an idler drum 46 to permit the drum 46 to revolve about the support shaft 43. Each slack and guide adjuster 44 is constructed and functions similarly to the adjusters 28, described previously in connection with the conveyor means 20, for removing any excessive slack in the abrasive belt 45 and for guiding or tracking the belt 45.

The constant load means 50 pivotably supported by said side frames l3, l4 and located along said predetermined path on a side of the conveyor belt 34 opposite said abrading assembly, as more clearly shown in FIGS. 1, 4 and 5, includes a movable substantially flat bed 51 connected at a first end, to an end of the block support 17 by universally pivotable means, e. g. a ball-and-socket connection 52, and supported by pivotal connections on a constant force means 53 located removed from said pivotable means. The substantially flat bed 51 receives a concrete block 11 and upon engagement between the block 11 and the abrading assembly 35, the ball-andsocket 52 affords the bed 51 to pivot about a longitudinal axis to accommodate the bed 51 to a transverse taper of either or both opposed facial surfaces 19, 19a of block 11. Thus, the block 1 1 is rotated about a longitudinal axis to orient and align the transverse portion of the facial surface 19 adjacent to contact drum 39 substantially parallel to the transverse axis of the drum 39. Also, as a block 11 having a longitudinal convex or concave shape, as shown in FIGS. 6, 7 and 8, of the facial surface 19 adjacent the assembly 35 is moved past the abrading assembly 35, the ball-and-socket 5.2 affords the bed 51 to pivot about a transverse axis to accommodate the bed 51 to longitudinal variations on the facial surface 19 of said block I l.

The bed 51, as shown in the drawings, is oriented with the blocks 11 first contacting the second end portion of the bed 51. adjacent to the constant force means 53, and lastly contacting the first end portion of the bed 51, adjacent the balland-socket 52. This orientation is not controlling and the blocks 11 could travel in the opposite direction across the bed 51 with little appreciable difference in the performance of the constant load means 50.

The constant force means 53, which is shown as comprising fluid cylinders 54, air cylinders in the preferred embodiment, could be located at any practical distance from the ball-andsocket 52 and is shown located at the second end of the bed 51 for obtaining greater mechanical advantage. Each air cylinder 54, 54 is pivotably mounted to each side frame 13, 14 via the ball-and-socket connections 55 and pivotably mounted to the bed via the ball-and-socket connections 56. The connections 55 and 56 afford free movement of the bed to accommodate irregularly shaped blocks in either a transverse or longitudinal direction. To restrain the lateral motion of the bed 51, a guide pin 57, see FIG. 5, is secured to the bed 51 and slidably engages the slide guide 58 which is secured to the side frames 13, 14..

Thus, pivotable movement of the constant load means 50 about the longitudinal axis serves to maintain line contact of the block with the abrasive material transversely across the facial surface 19. Movement of the bed about the transverse axis affords contact longitudinal of the block as it is moved past the abrasive material. The cylinders 54 maintain a constant predetermined loading force 72 on the block 11 against the abrasive material to control the grinding depth.

The holding means 60, which is supported from said constant load means 50 and spaced from said abrading assembly 35, restrains tipping movement of a block about itself caused by engagement with said abrasive material or belt 45, and includes two shafts 61, 61 fixed to bed 51, two upper stops 62, 62 two lower stops 63, 63, two slidable collars 64, 64 (one on each shaft 61), a transverse shaft 65 extending between and supported by the collars 64, 64, a pinch roll 66, and two springs .67 to force the pinch roll 66 against the block 1 1 being abraded. With the direction of the abrasive belt 45 moving as shown by arrow 68, the engaging force between the block 11 and the abrasive belt 45 would tend to tip the block 11 in a counterclockwise direction, as shown in FIG. 3. The counterclockwise engaging force is offset by the clockwise reactive force of the holding means 60 against the block 11. If the block was passed through the abrading assembly 35 in a direction from front to rear or if the abrasive material was moved in a direction opposite to arrow 68, then the holding means 60a, which is constructed similarlyto holding means 60, would restrain any tipping of the block 11.

Each air cylinder 54 includes air lines and a pressure regulator (not shown) for achieving a constant predetermined force 71, see the force diagram of FIG. 6. The loading force 72, which is directly proportional to the depth of the grind, is independent of the pinch forces 73 caused by the interference of the block 11 between the pinch rolls 66, 66a and the bed 51. Thus, as an irregularly shaped block 11 is moved past the abrading assembly 35, the constant predetermined force 71 and the movable bed 51 maintains a constant predetermined loading force 72 in continuous transverse line contact and progressive longitudinal contact between the abrasive material and the facial surface 19 of the block 11 to minimize the removal of material required to permit all portions of said facial surface 19 to be abraded to at least a predetermined grinding depth for aesthetic decorative effects.

I claim:

1. A grinding apparatus block, comprising:

a. a frame;

b. conveyor means movable over said frame for moving a said block along a predetermined longitudinal path; c. an abrading assembly supported by said frame and located adjacent to said conveyor means and along said predetermined longitudinal path, including l. a substantially rigid cylindrical surface having a fixed axis of rotation extending transverse to said longitudinal path,

2. an abrasive material supported by said cylindrical surface, and

3. drive means for moving said abrasive material at a relatively high surface speed;

for abrading a facial surface of a d. a load bed located along said predetermined path opposite said abrading assembly and pivotably supported by said frame around a longitudinal axis to accommodate said load bed to a said block having a transverse taper to maintain transverse line contact across a said block;

e. constant force means connected to said bed and said frame for forcing said facial surface against said abrasive material and thus afford a uniform grinding depth across said facial surface; and

f. holding means supported by said load bed and spaced from said cylindrical surface to restrain tipping movement of a said block about itself caused by engagement with said abrasive material.

2. A grinding apparatus as defined in claim 1 wherein said conveyor means includes a. a conveyor belt;

b. motor means for moving said belt at a predetermined speed; and

c. a cleat connected to said belt to engage said block and thus minimize any relative motion between said block and said conveyor belt. I

3. A grinding apparatus as defined in claim 2 wherein said abrading assembly includes a. a cylindrical contact drum having a fixed axis of rotation extending transverse to said longitudinal path and having a substantially rigid surface b. an idler drum;

c. an abrasive belt extending about said contact drum and said idler drum; and

d. drive means connected to said contact drum for driving said abrasive belt at a relatively high surface speed.

4. A grinding apparatus as defined in claim 3 wherein said load bed includes a. a substantially flat bed;

b. pivotable means connecting the first end portion of said bed to said frame for permitting rotational movement of said bed about both a transverse and a longitudinal axis to accommodate varying geometric shapes of said block; and wherein c. said constant force means is located removed from said first end portion and pivotably connected to said bed for loading said block at a predetermined force in transverse line contact against said abrasive material to control the grinding depth transversely across the facial surface of said block.

5. A grinding apparatus as defined in claim 4 wherein the longitudinal distance between that part of said contact drum nearest said conveyor belt and the upstream end of said fiat bed is at least equal to the length of said block to afford locating of said block on said bed prior to engagement of said block with said abrasive material.

6. A grinding apparatus as defined in claim 4 wherein said constant force means includes a fluid cylinder to maintain a constant loading force of said block against said abrasive belt.

7. A grinding apparatus as defined in claim 4 wherein said constant force means includes two fluid cylinders each laterally spaced from said pivotable means to maintain a constant loading force of said block against said abrasive belt. 

1. A grinding apparatus for abrading a facial surface of a block, comprising: a. a frame; b. conveyor means movable over said frame for moving a said block along a predetermined longitudinal path; c. an abrading assembly supported by said frame and located adjacent to said conveyor means and along said predetermined longitudinal path, including
 1. a substantially rigid cylindrical surface having a fixed axis of rotation extending transverse to said longitudinal path,
 2. an abrasive material supported by said cylindrical surface, and
 3. drive means for moving said abrasive material at a relatively high surface speed; d. a load bed located along said predetermined path opposite said abrading assembly and pivotably supported by said frame around a longitudinal axis to accommodate said load bed to a said block having a transverse taper to maintain transverse line contact across a said block; e. constant force means connected to said bed and said frame for forcing said facial surface against said abrasive material and thus afford a uniform grinding depth across said facial surface; and f. holding means supported by said load bed and spaced from said cylindrical surface to restrain tipping movement of a said block about itself caused by engagement with said abrasive material.
 2. an abrasive material supported by said cylindrical surface, and
 2. A grinding apparatus as defined in claim 1 wherein said conveyor means includes a. a conveyor belt; b. motor means for moving said belt at a predetermined speed; and c. a cleat connected to said belt to engage said block and thus minimize any relative motion between said block and said conveyor belt.
 3. drive means for moving said abrasive material at a relatively high surface speed; d. a load bed located along said predetermined path opposite said abrading assembly and pivotably supported by said frame around a longitudinal axis to accommodate said load bed to a said block having a transverse taper to maintain transverse line contact across a said block; e. constant force means connected to said bed and said frame for forcing said facial surface against said abrasive material and thus afford a uniform grinding depth across said facial surface; and f. holding means supported by said load bed and spaced from said cylindrical surface to restrain tipping movement of a said block about itself caused by engagement with said abrasive material.
 3. A grinding apparatus as defined in claim 2 wherein said abrading assembly includes a. a cylindrical contact drum having a fixed axis of rotation extending transverse to said longitudinal path and having a substantially rigid surface b. an idler drum; c. an abrasive belt extending about said contact drum and said idler drum; and d. drive means connected to said contact drum for driving said abrasive belt at a relatively high surface speed.
 4. A grinding apparatus as defined in claim 3 wherein said load bed includes a. a substantially flat bed; b. pivotable means connecting the first end portion of said bed to said frame for permitting rotational movement of said bed about both a transverse and a longitudinal axis to accommodate varying geometric shapes of said block; and wherein c. said constant force means is located removed from said first end portion and pivotably connected to said bed for loading said block at a predetermined force in transverse line contact against said abrasive material to control the grinding depth transversely across the facial surface of said block.
 5. A grinding apparatus as defined in claim 4 wherein the longitudinal distance between that part of said contact drum nearest said conveyor belt and the upstream end of said flat bed is at least equal to the length of said block to afford locating of said block on said bed prior to engagement of said block with said abrasive material.
 6. A grinding apparatus as defined in claim 4 wherein said constant force means includes a fluid cylinder to maintain a constant loading force of said block against said abrasive belt.
 7. A grinding apparatus as defined in claim 4 wherein said constant force means includes two fluid cylinders each laterally spaced from said pivotable means to maintain a constant loading force of said block against said abrasive belt. 